With development of Ethernet network towards multi-service bearing direction, in particular, some of services have an increasing requirement for the reliability, real-time of the network, and Ethernet widely adopts ring networking so as to improve network reliability. Furthermore, in the ring protection method, it usually requires fast protection switching, reaching below 50 ms. At present, such fast protection switching technology includes RFC3619 of Internet Engineering Task Force (IETF) and G.8032 of International Telecommunications Union (ITU-T), etc.
With regard to the definition of a sub-ring, the standards being established in the international, such as G.8032 of ITU, considers that the sub-ring is an Ethernet ring connected with other rings or networks by interconnection nodes, the interconnection node is a common node belonging to two or more Ethernet rings simultaneously.
As shown in FIG. 1a for instance, the nodes from A to G on the Sub-ring1 are the nodes having Ethernet switching function, and Sub-ring1 accesses the network X by the interconnection nodes. User M is connected with the node B, and user N is connected with the node D. Communication is between the user M and the user N. There are two physical paths between the user M and the user N, that is, user N←→node D←→node C←→node B←→user M, and user N←→node D←→node E←→node F←→network X←→node G←→node A←→node B←→user M.
When the Sub-ring protection technology is applied, it generally defines a ring protection link and a control node, namely: in the case of Ethernet ring network without failure, the ring protection link is a link that blocks data messages and prevents the formation of data link on the Sub-ring, and switching between the main path and the protection path of the Sub-ring can be performed through operating this section of the ring protection link. The node with the ring protection link is referred to as the control node or the main node herein. As shown in FIG. 2a, the ring network comprises nodes G, A, B, C, D, E and F, and comprises links <G, A>, <A, B>, <B, C>, <C, D>, <D, E> and <E, F>. The node A is the control node, and straight link <A, B> directly connected with w port of the node A is a ring protection link.
When the links on the ring are intact, the control node blocks the data message forwarding function of the port connected with the ring protection link, and there is no loop generating in the network, which prevents “broadcast storm” caused by the network loop. As shown in FIG. 2a, the control node A blocks the protection data forwarding function of w port, and the communication path between the user M and the user N is Path1: user M←→node B←→node C←→node D←→user N.
When link failure occurs, the control node unblocks the data message forwarding function of the port connected with the ring protection link, thereby ensuring the connection of the services. As shown in FIG. 2b, the failure of the link <B, C> on the ring occurs, the control node A unblocks the data message forwarding function of the port w, and the new communication path between the user M and the user N is Path2: user M←→node B←→node A←→node G←→network X←→node F←→node E←→node D←→user N.
When the link switching of Sub-ring occurs, the nodes need to refresh the address forwarding table so as to prevent the data message from keeping forwarding along the wrong path, i.e. the link before the link switching. As shown in FIG. 2a, when the ring network has no failure, the communication path between the user M and the user N is the Path1: user M←→node B←→node C←→node D←→user N. When the failure of the link <B, C> on the ring occurs, and if the nodes on the ring do not refresh the address, the data messages of the user M and the user N still transmit along the original path, the message sent by the user M is discarded at the node B, and the message sent by the user N is discarded at the node C. Therefore, in order to ensure the ring network is after topological change, the nodes on the ring network should refresh the address forwarding table.
Presently, the solution of refreshing the address of ITU-T G.8032 is that: when the port of the node on the Sub-ring receives a address refreshment protocol message, <Node_ID, BPR> information is extracted; this port compares the <Node_ID, BPR> information in the message with the <Node_ID, BPR> information originally stored in this port; if they are not consistent, this port deletes the originally stored <Node_ID, BPR> and stores the new <Node_ID, BPR>, and at the same time, the node refreshes the address forwarding table. The NODE_ID is an identification number of the node, and the BPR is used to indicate which port that sends the protocol message is blocked.
The address refreshment message of the Sub-ring should be transmitted on the Sub-ring control channel. Presently, the Sub-ring control channel of ITU-T G.8032 has two configuration ways. One is a configuration way without virtual channel, i.e., the Sub-ring control channel is only configured within the Sub-ring, as shown in FIG. 3a. Another Sub-ring control channel configuration includes a part of the Sub-ring and virtual channel. The virtual channel is configured on the other network or other ring between the interconnection node, and the virtual channel is a Sub-ring control channel that provides transmission channel for the Sub-ring protocol message, as shown in FIG. 3b. In the present invention, we mainly describe a method for transmitting the protocol message on a Sub-ring control channel without virtual channel. Wherein, the other ring includes the other Sub-ring.
Currently, the provision of blocking the Sub-ring protocol message by the G.8032 is that: “in the case of no virtual channel, the Sub-ring control channel terminates at the interconnection nodes, and the node on the ring blocks the transmission of the protocol message of the Sub-ring control channel”.
The above solution of the Sub-ring control channel transmitting the protocol message will encounter problems in the following scenario, which is described specifically as follows:
as shown in FIG. 4a, e port of the node C initiates a forced switch (FS), the node C refreshes the address forwarding table, and then outwardly sends an FS protocol message along the two ports on the Sub-ring periodically. After other nodes on the Sub-ring firstly receive the protocol message, they refresh respective address forwarding table, and the control node A also unblocks the forwarding function of data message of w port. In the FIG. 4b, a single-pass failure of the link <E, D> occurs, that is: the direction of E→D is unblocked and the direction of D→E is blocked; the node E blocks e port and outwardly sends an SF message. Since non-failure block point on the Sub-ring just blocks data and does not block the protocol message, nodes A, B and G alternately receive the FS and SF protocol messages sent by the node C and the node E. the <Node_ID, BPR> stored by the nodes A, B and G will refresh continuously along with the alternately receiving of the FS and SF protocol messages of nodes. In other words, the nodes A, B and G are in a continuous refresh state. The Sub-ring performance is greatly damaged, and is always in a broadcast storm.